1. Field of the Invention
This invention relates to an ink jet recording head which discharges ink from a discharge port and effects recording of images on a recording medium, and in particular to an ink jet recording head provided with a discharge port forming member formed with said discharge port.
The present invention also relates to an ink jet recording apparatus having an ink jet recording head provided with said discharge port forming member.
2. Related Background Art
FIG. 1 of the accompanying drawings is a perspective view schematically showing the external construction of an ink jet recording apparatus. In FIG. 1, the reference numeral 1 designates an ink jet recording head (hereinafter referred to as the recording head) which discharges ink on the basis a predetermined recording signal and records a desired image, and the reference numeral 2 denotes a carriage carrying the recording head 1 thereon and which is scan-moved in the direction of a record line (the main scanning direction). The carriage 2 is slidably supported by guide shafts 3 and 4, and is reciprocally moved in the main scanning direction in operative association with a timing belt 8. The timing belt 8 engaged with pulleys 6 and 7 is driven by a carriage motor 5 through the pulley 7.
Recording paper 9 is guided by a paper pan 10 and conveyed by a paper feeding roller, not shown, urged by a pinch roller. This conveyance is effected with a paper feeding motor 16 as a drive source. The recording paper 9 thus conveyed has tension imparted thereto by a paper discharge roller 13 and a spur 14 and is urged against a heater 11 by a paper keep plate 12 formed by a resilient member and therefore, it is conveyed while being brought into intimate contact with the heater 11. The recording paper 9 to which ink injected by the head 1 adheres is warmed by the heater 11 and the ink adhering thereto has its water content evaporated and is fixated on the recording paper 9.
The reference numeral 15 designates a unit called a recovery system. The unit 15 removes any foreign substance or viscosity-increased ink adhering to the discharge port of the recording head 1, thereby maintaining the discharge characteristic in its state.
On the recording area side of the recovery system unit 15, there is provided a cleaning blade 17 for bearing against the surface of the recording head 1 in which the discharge port is formed and removing any foreign substance or ink droplets adhering to the discharge port surface.
The recording head 1 carried on the aforedescribed ink jet recording apparatus, as shown in FIGS. 2 and 3 of the accompanying drawings, is comprised of a discharge port forming member 26 (hereinafter referred to as the orifice plate) formed with a plurality of minute ink discharge ports 27, and a head body 29 provided with ink paths 24 communicating with said discharge ports 27. Some of the ink paths 24 are provided with ink discharge energy generating members (not shown) utilized to discharge the ink from the discharge ports 27.
For example, where heat energy generating elements generating heat energy are used as the energy generating members, the ink is discharged from the discharge ports by the utilization of a sudden pressure change caused by a bubble created by the heat energy. In order that it may be carried on the ink jet recording apparatus, the recording head 1 is of such a construction as shown in FIG. 3 wherein a head support member 32 and a front plate holder 30 are assembled together and the space between the head body 29 and the front plate holder 30 is sealed by a sealing agent 31.
In the recording head 1 of such a construction, an orifice plate having an area substantially equal to or slightly smaller than that of the coupled surface of the head body 29 has been employed as the orifice plate 26 formed with the discharge ports.
When recording is effected with such recording head 1 carried on the ink jet recording apparatus, ink droplets and foreign substances may sometimes adhere to the discharge port surface, and this has caused the ink discharge characteristic to be deteriorated. In order to eliminate such a cause, as previously described, it has been practised to cause the cleaning blade 17 provided in the ink jet recording apparatus to bear against the discharge port surface and clean the discharge port surface.
However, as shown in FIGS. 4A-4C of the accompanying drawings, the orifice plate 26 forming the discharge port surface of the recording head 1 has sometimes been damaged by the cleaning operation performed when the recording head 1 (which has completed its recording operation) has been moved to the area in which the recovery unit 15 and the cleaning blade 17 are provided. That is, by the cleaning operation for the discharge port surface, strong mechanical pressure is exerted on the joined surface between the orifice plate 26 and the head body 29 in the end portion wherein the cleaning blade 17 bears against the orifice plate forming the discharge port surface.
By this cleaning operation being repeated, as shown in FIGS. 4B and 4C, the orifice plate 26 may peel off in the end portion thereof which is joined to the head body 29, or the adhesive agent which joins the orifice plate 26 to the head body 29 and covers the side portion of the orifice plate 26 may peel off.
If the orifice plate or the adhesive agent thus peels off, it may adversely affect the accuracy of ink discharge and cause disturbance of recorded images.
Also, as shown in FIG. 3, the recording head 1 adopts a construction having the front plate holder 30 which provides a receiving surface for a nozzle suction cap mechanism (recovery unit) utilized in the recovery operation performed to protect the orifice plate 26, prevent the ink from going round to the electrical wiring portion and eliminate any bubble embraced in the nozzle or eliminate unsatisfactory discharge. In this case, to obtain full display of the aforementioned functions, it is necessary to seal and fix all the gap between the opening in the front plate holder 30 in which the head body 29 is mounted and the head body 29.
However, there is the possibility that mechanical pressure produced by the cleaning blade 17 bearing against the front plate holder 30 when cleaning the discharge port surface of the recording head 1 is exerted on the front plate holder 30 to cause positional deviation thereof. Also, when positional deviation of the front plate holder 30 is caused, there is formed a gap between the front plate holder 30 and the head body 29 and thus, a hermetically sealed space cannot be formed when the recovery operation is performed, and the recovery operation cannot sometimes be sufficiently performed. Further, when the gap is formed as previously mentioned, there is the possibility that the ink adhering to the front face of the recording head 1 goes round through the gap to the rear of the head body. If the ink goes round to the rear of the head body and arrives at the electrical connecting portion between the ink jet recording apparatus and the recording head 1, unsatisfactory electrical connection will be caused and it will become impossible to accomplish desired recording.